1. Field of the Invention
The present invention is related to receivers for frequency shift keying (FSK) modulated signals.
2. Background
Frequency shift keying (FSK) modulation changes the frequency of a signal over a time period to represent different values of a bit. For example, in the case of binary FSK modulation, a bit “0” is represented by a sine wave with frequency f0 over one bit period and a bit “1” is represented by a sine wave of frequency f1.
While widely used, existing FSK receivers suffer serious limitations. For example, existing FSK receivers use fixed local oscillators, have no baseband filtering prior to frequency discrimination, and use fixed bandwidth data filters prior to bit detection that limits performance and flexibility. Furthermore, all signal processing is done in the analog domain, and RF gain stages within receivers are not programmable. These constraints further limit the robustness and flexibility of FSK receivers. Additionally, existing FSK receivers are not integrated onto a larger system chip, but typically make up a standalone chip with many peripheral discrete components. As a result, existing FSK receivers are relatively expensive. Finally traditional burst FSK receivers use an asynchronous architecture with no correlators for preamble or data detection, and no symbol timing recovery further limiting receiver robustness.
Therefore, what is needed is a robust integrated burst FSK receiver that operates cost effectively over a wide range of applications.